Michele Capobianco

Approaches to long-term modelling of coastal morphology: A review

Aspects of long-term mathematical modelling of coastal morphology are inventoried and discussed. They concern reduction techniques for input data, process descriptions and output data, as well as model concepts ranging from statistical extrapolation of the past coastal behaviour, via semi-empirical behaviour models, to formally integrated descriptions of the constituent small-scale processes. All approaches have in common that they reduce the need for detailed descriptions in space and time of the underlying physical processes. They lead not only to more transparent and robust models which require less computational effort, but also to a better insight into which aspects of coastal behaviour are relevant from a long-term point of view and which are not (“signal” vs. “noise”).

Beach nourishment projects, practices, and objectives—a European overview

The uses of beach fill in the countries of the European Union are highlighted and discussed with respect to the general situation, project type and objectives, design and evaluation procedures, legal framework, and financial aspects. As expected, significant differences were found among the investigated countries. In general, the study shows that it would be very profitable for south European countries to learn about the Dutch and German practices, particularly regarding the long-term coastal management and the regular monitoring of the coastal morphology. On the other hand, recent Dutch experience has shown that their legal system is a bit rigid, leading sometimes to renourishments that are less necessary to reach the global objective.

Variability of shore and shoreline evolution

Shore and shoreline evolution both due to natural and human-induced causes or factors can be variable over a wide range of different temporal and/or spatial scales. Our capability to understand and especially predict this variability is still limited. This can lead to misinterpretation of coastal change information, which hampers informed decision making and the subsequent design and implementation of (soft) engineering interventions. Collecting and describing example observations of shore and shoreline variability is one way to support and improve such human intervention. This paper describes causes and factors for the variability and the resulting possible evolutions of wave-dominated shores and shorelines, which are illustrated by a number of case studies. The new element of this work is that the variability is described in terms of a range of different time and space scales, which helps to structure such analysis. However, it is difficult to generalise the results for arbitrary situations, especially on decadal time scales. Scientific and engineering improvements require more quantitative insight into the physical mechanisms behind the free and forced shore behaviour responsible for the variability.

Relationship between beach profiles and waves at Duck, North Carolina, determined by canonical correlation analysis

Abstract An 11-year long measurement time series of waves and profiles from Duck, North Carolina, was analyzed using canonical correlation analysis (CCA) in order to determine the covariability between waves and profile response. The main objectives of this analysis were (1) to detect simultaneously occurring patterns in the wave and profile data and, if possible, give such patterns a physical interpretation to increase the insight into the governing processes, and (2) to investigate the possibility to use CCA in a predictive mode with the aim to calculate the profile response from the waves. The profile shape itself and the change between consecutively surveyed profiles were correlated with both the offshore (deep-water) and nearshore wave conditions. In the offshore, the waves were described by composite probability density functions (pdf) derived based on the measured wave conditions prior to a profile survey. Nearshore wave conditions were calculated using a random breaker decay model and averaged local wave properties were used as input to the CCA. The profile response displayed significantly higher correlation with the nearshore wave properties as compared to the offshore waves, and the highest correlation was found between the profile shape and the mean ratio of breaking waves for the time period preceding the profile survey. The CCA using nearshore wave properties indicates a potential for predicting the profile response with an acceptable degree of accuracy once a regression matrix relating the profiles to the waves has been established that represents the typical variability at the site.

Shoreline evolution of the Holland coast on a decadal scale

The decadal evolution of the dunefoot position along 120 km of the Holland coast is analysed. Firstly, a new definition of dunefoot is introduced based on hydrodynamic and morphologic considerations, which is not affected by local and instantaneous processes occurring immediately before the bathymetric survey. The dunefoot evolution over decadal scales indicates the existence of spatial and temporal oscillations in the shoreline position with magnitudes of 2–3 km length and a periodicity of 4–15 years. Two main controlling factors of this behaviour are identified: (1) influence of sub-aqueous bar systems, and (2) changes in the storm-wave conditions reaching the coast. Although the precise controlling processes of the relation between the dunefoot and the subaqueous profile still remain unclarified, we introduce the concept that the development of a morphological bar cycle requires a fixed amount of time-integrated forcing that is proportional to the cumulative effect of storm waves. Beach mobility along the Holland coast on decadal scales (10–20 m) is similar or lower than mobility introduced by storms or by seasonal cycles. However, it is important to consider these changes for the possible implications on the local vulnerability of the coast to extreme events. Copyright

Impacts of sea-level rise on the Ebro Delta: a first approach

Global climatic change is taking place and it will likely affect Mediterranean deltas and other low-lying coastal regions in terms of sea-level rise, salinity increase and changes in temperature and weather patterns. This will have serious implications because these deltas are very valuable in terms of natural resources and related economic activities. This study focuses on one of the northwestern Mediterranean deltas, namely that of the Ebro river. There is an enormous lack of information about and understanding of the integral functioning of this type of system. The objective of this ongoing study is to determine the vulnerability and response of this deltaic system to climate change, such that informed decision-making can be made. In order to do this it is proposed to make combined use of existing and new field measurements (sedimentation, soil formation and coastal fringe response) and an integrated (physical/ecological) conceptual model of deltaic behaviour. Using these tools, organized in relation to the interaction with socio-economic components, a number of intervention scenarios, aiming to cope with the effects of climate change, will be examined in a later stage of the research project. It is expected that these results will provide valuable information for integrated, comprehensive approaches to determine whether management plans are sustainable.

DEPTH OF CLOSURE: IMPROVING UNDERSTANDING AND PREDICTION

Detailed studies have been undertaken to assist in the design of major extensions to the port of Haifa. Both numerical and physical model studies were done to optimise the mooring conditions vis a vis the harbour approach and entrance layout. The adopted layout deviates from the normal straight approach to the harbour entrance. This layout, together with suitable aids to navigation, was found to be nautically acceptable, and generally better with regard to mooring conditions, on the basis of extensive nautical design studies.Hwa-Lian Harbour is located at the north-eastern coast of Taiwan, where is relatively exposed to the threat of typhoon waves from the Pacific Ocean. In the summer season, harbour resonance caused by typhoon waves which generated at the eastern ocean of the Philippine. In order to obtain a better understanding of the existing problem and find out a feasible solution to improve harbour instability. Typhoon waves measurement, wave characteristics analysis, down-time evaluation for harbour operation, hydraulic model tests are carried out in this program. Under the action of typhoon waves, the wave spectra show that inside the harbors short period energy component has been damped by breakwater, but the long period energy increased by resonance hundred times. The hydraulic model test can reproduce the prototype phenomena successfully. The result of model tests indicate that by constructing a jetty at the harbour entrance or building a short groin at the corner of terminal #25, the long period wave height amplification agitated by typhoon waves can be eliminated about 50%. The width of harbour basin 800m is about one half of wave length in the basin for period 140sec which occurs the maximum wave amplification.Two-stage methodology of shoreline prediction for long coastal segments is presented in the study. About 30-km stretch of seaward coast of the Hel Peninsula was selected for the analysis. In 1st stage the shoreline evolution was assessed ignoring local effects of man-made structures. Those calculations allowed the identification of potentially eroding spots and the explanation of causes of erosion. In 2nd stage a 2-km eroding sub-segment of the Peninsula in the vicinity of existing harbour was thoroughly examined including local man-induced effects. The computations properly reproduced the shoreline evolution along this sub-segment over a long period between 1934 and 1997.In connection with the dredging and reclamation works at the Oresund Link Project between Denmark and Sweden carried out by the Contractor, Oresund Marine Joint Venture (OMJV), an intensive spill monitoring campaign has been performed in order to fulfil the environmental requirements set by the Danish and Swedish Authorities. Spill in this context is defined as the overall amount of suspended sediment originating from dredging and reclamation activities leaving the working zone. The maximum spill limit is set to 5% of the dredged material, which has to be monitored, analysed and calculated within 25% accuracy. Velocity data are measured by means of a broad band ADCP and turbidity data by four OBS probes (output in FTU). The FTUs are converted into sediment content in mg/1 by water samples. The analyses carried out, results in high acceptance levels for the conversion to be implemented as a linear relation which can be forced through the origin. Furthermore analyses verifies that the applied setup with a 4-point turbidity profile is a reasonable approximation to the true turbidity profile. Finally the maximum turbidity is on average located at a distance 30-40% from the seabed.

Towards the definition of budget models for the evolution of deltas

Global climatic change is likely to take place and could eventually affect Mediterranean deltas and other lowlying coastal regions. This would have serious implications for the natural resources of these deltaic areas, as well as for human settlements and related economic activities.To achieve sound decision making, to prevent damages and to avoid risky investments, it is necessary to understand the integral functioning of deltaic areas and to determine their vulnerability and response to large-scale change phenomena. Optimal use of the available knowledge will require that existing and new field measurements are combined and that integrated (physical/ecological) conceptual models of deltaic behaviour are developed with socio-economics scenarios as boundary conditions.This paper illustrates the methodological effort towards organizing a modeling framework to conduct budget computations at various scales with reference to the most significant ‘physiogrpahic units’ and to the most significant deltaic processes. The final objective is to handle the problem of evaluating possible changes under different scenarios.

Bar migration and duneface oscillation on decadal scales

A study of alternatives including a shoreline evolution numerical modelization has been carried out in order to both diagnose the erosion problem at the beaches located between Cambrils Harbour and Pixerota delta (Tarragona, Spain) and select nourishment alternatives.

MODEL TESTS FOR EVALUATING BEACH NOURISHMENT PERFORMANCE

Detailed studies have been undertaken to assist in the design of major extensions to the port of Haifa. Both numerical and physical model studies were done to optimise the mooring conditions vis a vis the harbour approach and entrance layout. The adopted layout deviates from the normal straight approach to the harbour entrance. This layout, together with suitable aids to navigation, was found to be nautically acceptable, and generally better with regard to mooring conditions, on the basis of extensive nautical design studies.Hwa-Lian Harbour is located at the north-eastern coast of Taiwan, where is relatively exposed to the threat of typhoon waves from the Pacific Ocean. In the summer season, harbour resonance caused by typhoon waves which generated at the eastern ocean of the Philippine. In order to obtain a better understanding of the existing problem and find out a feasible solution to improve harbour instability. Typhoon waves measurement, wave characteristics analysis, down-time evaluation for harbour operation, hydraulic model tests are carried out in this program. Under the action of typhoon waves, the wave spectra show that inside the harbors short period energy component has been damped by breakwater, but the long period energy increased by resonance hundred times. The hydraulic model test can reproduce the prototype phenomena successfully. The result of model tests indicate that by constructing a jetty at the harbour entrance or building a short groin at the corner of terminal #25, the long period wave height amplification agitated by typhoon waves can be eliminated about 50%. The width of harbour basin 800m is about one half of wave length in the basin for period 140sec which occurs the maximum wave amplification.Two-stage methodology of shoreline prediction for long coastal segments is presented in the study. About 30-km stretch of seaward coast of the Hel Peninsula was selected for the analysis. In 1st stage the shoreline evolution was assessed ignoring local effects of man-made structures. Those calculations allowed the identification of potentially eroding spots and the explanation of causes of erosion. In 2nd stage a 2-km eroding sub-segment of the Peninsula in the vicinity of existing harbour was thoroughly examined including local man-induced effects. The computations properly reproduced the shoreline evolution along this sub-segment over a long period between 1934 and 1997.In connection with the dredging and reclamation works at the Oresund Link Project between Denmark and Sweden carried out by the Contractor, Oresund Marine Joint Venture (OMJV), an intensive spill monitoring campaign has been performed in order to fulfil the environmental requirements set by the Danish and Swedish Authorities. Spill in this context is defined as the overall amount of suspended sediment originating from dredging and reclamation activities leaving the working zone. The maximum spill limit is set to 5% of the dredged material, which has to be monitored, analysed and calculated within 25% accuracy. Velocity data are measured by means of a broad band ADCP and turbidity data by four OBS probes (output in FTU). The FTUs are converted into sediment content in mg/1 by water samples. The analyses carried out, results in high acceptance levels for the conversion to be implemented as a linear relation which can be forced through the origin. Furthermore analyses verifies that the applied setup with a 4-point turbidity profile is a reasonable approximation to the true turbidity profile. Finally the maximum turbidity is on average located at a distance 30-40% from the seabed.